System for rinsing and drying semiconductor substrates and method therefor

ABSTRACT

A system and method for cleaning and drying semiconductor wafers improves device yield by providing more advanced control of the ratio of drying fluid to cleaning fluid, for example the ratio of N 2  vapor to IPA vapor. In addition, a quick drain process is employed to improve process throughput, and to further improve particle and watermark removal during the cleaning and drying steps.

BACKGROUND OF THE INVENTION

During the manufacture of semiconductor devices arranged in arrays onwafer substrates, the wafers are subjected to various chemicaltreatments. The treatments are in the form of a number of process stepsthat the wafers undergo during the formation of devices, including theformation of, processing of, and removal of, layers, photolithographyprocesses, and the like. Following certain steps, extraneous particlescan remain on the substrate, which can have an adverse effect onsubsequent processes. In contemporary fabrication techniques, thesubstrates are rinsed and dried to remove such particles.

For rinsing the wafers, it is common to use deionized water (DI) or acommercial cleaning solution such as SC1. When drying the substrate,isopropyl alcohol (IPA) is commonly used. However, IPA-based dryingprocesses commonly leave particles and watermarks on the substrates. Toimprove the IPA-based drying process, a drying technique referred to asthe Marongoni technique, has become popular.

In the Marongoni technique, the wafers are slowly lifted out of the DIbath, or the DI bath is slowly drained. At this time, the exposed wafersare immersed in an IPA vapor. Since the concentration of the IPA vaporis highest at the interface with the DI bath, the resulting surfacetension of the water is low in this region. This results in a phenomenonreferred to as Marongoni flow of the DI water bath away from the wafersurfaces, thereby drying the wafer surfaces. While the Marongoniapproach is somewhat effective for removing particles from the wafers,because the slow drain procedure drastically reduces process throughput.For example, the drain time may be on the order of 225 seconds for a 12inch wafer. In addition, watermarks can remain on the substratefollowing a Marongoni flow procedure.

To improve the effectiveness of the removal of particles and watermarksby the IPA vapor, heated nitrogen gas N₂ can also be introduced into theprocess chamber. This technique is disclosed in U.S. Pat. No. 6,328,809,the content of which is incorporated herein by reference. With referenceto FIG. 1, in this approach, the IPA vapor is transported into a waferprocess chamber using a source of heated nitrogen gas. Referring to FIG.1, nitrogen from a nitrogen gas source N₂ flows through valve 11, isheated at heater 12, and flows through valve 15A into a tank 10containing IPA solution. The IPA solution is partially heated into avapor within the tank by heater 14. The pressure of the heated nitrogengas forces the combined nitrogen and IPA gases to flow through valve 15Cand into the process chamber 20. The combined IPA/N₂ gas is introducedinto the process chamber 20 to carry out an IPA decontaminating step.During this step, valve 15B is closed. Following this, heated N₂ gasflows directly into the process chamber by closing valves 15A and 15Cand opening valve 15B in a purge step, in order to volatize anycondensed IPA remaining on the wafers.

To ensure the removal of particles and watermarks, the ratio of nitrogengas to IPA gas in the process chamber is a critical factor during theIPA decontaminating step, since the ratio is closely correlated withdevice yield. However, control over this ratio is limited in theconventional approaches, since the nitrogen gas is used exclusively as atransport medium for the IPA gas during the decontaminating procedure.

SUMMARY OF THE INVENTION

The present invention is directed to a system and method for rinsing,decontaminating and drying semiconductor wafers in a manner thatimproves yield by providing more advanced control of the ratio of dryingfluid to cleaning fluid, for example the ratio of N₂ vapor to IPA vapor.In addition, a quick drain process is employed to improve processthroughput, and to further improve particle and watermark removal duringthe rinsing, decontamination, and drying steps.

In one aspect, the present invention is directed to a system forprocessing semiconductor wafers. A first inlet for a first supply ofdrying fluid is provided. A second inlet for a second supply of dryingfluid is also provided. The rate of supply of the second supply ofdrying fluid is independent of that of the first supply of drying fluid.A decontaminating fluid tank stores a supply of decontaminating fluid,the decontaminating fluid tank having an inlet for receiving the secondsupply of drying fluid, and having an outlet for supplyingdecontaminating fluid at a rate that is based on the rate of supply ofthe second supply of drying fluid. A process chamber houses thesemiconductor wafers to be cleaned and dried. The process chamberincludes an inlet for simultaneously receiving the first supply ofdrying fluid and the supply of decontaminating fluid.

The first supply of drying fluid and second supply of drying fluidcomprise, for example, nitrogen gas. A first heater may be provided forheating the first supply of drying fluid between the first inlet and theprocess chamber. A second heater may be provided for heating the secondsupply of drying fluid between the second inlet and the decontaminatingfluid tank.

A third heater may be coupled to the decontaminating fluid tank forheating the decontaminating fluid in the tank. The decontaminating fluidin the tank is partially heated by the third heater from a liquid into avapor and the second supply of drying fluid drives the decontaminatingfluid vapor through the outlet of the decontaminating fluid tank. Theinlet of the decontaminating fluid tank may include a first inlet forreceiving the second supply of drying fluid at a level below the levelof the liquid and a second inlet for receiving the second supply ofdrying fluid at a level above the level of the liquid.

A fourth heater may be coupled to a line in turn coupled to the inlet ofthe process chamber for heating the first supply of drying fluid and thesupply of decontaminating fluid prior to their release into the processchamber.

The first supply of drying fluid and the supply of decontaminating fluidreceived at the process chamber are preferably in a vapor state.

A coupling tube may be provided for selectively coupling the firstsupply of drying fluid to the decontaminating fluid tank. In addition, acoupling tube may be provided for selectively coupling the second supplyof drying fluid directly to the process chamber. Also, a coupling tubemay be provided for selectively coupling the first inlet to the secondinlet.

The process chamber further comprises a drain, and a buffer tank iscoupled to the drain of the process chamber. In one embodiment, thedrain comprises a plurality of drains, and the plurality of drains arecoupled to the buffer tank. The plurality of drains are, for example, ofa width to ensure rapid draining of the process chamber, for examplewithin a time period less than about 50 seconds, or, for example, withina time period ranging between about 7 and 17 seconds. The multipledrains are spaced apart in the process chamber to ensure that a topsurface of a fluid to be drained from the process chamber remains levelas the process chamber is drained. The buffer tank is preferably of avolume that is greater than or equal to the volume of the processchamber.

A first supply rate controller is provided for controlling the rate ofsupply of the first drying fluid and a second supply rate controller isprovided for controlling the rate of supply of the second drying fluid,the first and second supply rate controllers being independent of eachother such that the rate of supply of the first drying fluid and therate of supply of the second drying fluid are independent relative toeach other.

The process chamber may further comprise a plurality of exhaust portsdistributed in the process chamber to provide for laminar flow of thedecontaminating fluid and the drying fluid in the process chamber.

In another aspect, the present invention is directed to a method forprocessing semiconductor wafers. A first supply of drying fluid isprovided and a second supply of drying fluid is also provided. The rateof supply of the second supply of drying fluid is independent of that ofthe first supply of drying fluid. A supply of decontaminating fluid isstored in a decontaminating fluid tank. The decontaminating fluid tankhas an inlet for receiving the second supply of drying fluid, and has anoutlet for supplying decontaminating fluid at a rate that is based onthe rate of supply of the second supply of drying fluid. The firstsupply of drying fluid and the supply of decontaminating fluid aresimultaneously supplied to a process chamber to decontaminatesemiconductor wafers contained therein.

Prior to simultaneously supplying the first supply of drying fluid andthe supply of decontaminating fluid to the process chamber, rinsingfluid, for example DI water, is supplied into the process chambercontaining the semiconductor wafers for rinsing the semiconductorwafers. The rinsing fluid is then rapidly drained from the processchamber, for example into a buffer tank.

In a preferred embodiment, the rinsing fluid is completely drained priorto simultaneously supplying the first supply of drying fluid and thesupply of decontaminating fluid to the process chamber.

Following simultaneously supplying the first supply of drying fluid andthe supply of decontaminating fluid to the process chamber, a dryingfluid, for example nitrogen gas, is supplied into the chamber for dryingthe semiconductor wafers.

Throughout the present specification and claims, the term “fluid” isused herein in a manner consistent with its historical definition, andtherefore includes any non-solid form of matter, for example gases,vapors, and liquids.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the more particular description ofpreferred embodiments of the invention, as illustrated in theaccompanying drawings in which like reference characters refer to thesame parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 is a schematic block diagram of a conventional cleaning anddrying system for cleaning and drying semiconductor wafers.

FIG. 2 is a block diagram of a cleaning and drying system, in accordancewith the present invention.

FIG. 3 is a schematic block diagram of a first cleaning and dryingsystem for cleaning and drying semiconductor wafers in accordance withthe present invention.

FIG. 4 is a schematic block diagram of a second cleaning and dryingsystem for cleaning and drying semiconductor wafers in accordance withthe present invention.

FIG. 5 is a block diagram of a process chamber draining system inaccordance with the present invention.

FIG. 6 is a chart illustrating remanent particle density as a functionof the rate of flow of nitrogen vapor, in accordance with the presentinvention.

FIG. 7 is a chart illustrating remanent particle density as a functionof drain time, in accordance with the present invention.

FIG. 8 is a chart that illustrates the selection of optimal flow ratesfor the carrier nitrogen vapor and the purge nitrogen vapor, inaccordance with the present invention.

FIG. 9 is a flow diagram of a wafer cleaning and drying process, inaccordance with the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 2 is a block diagram of a cleaning and drying system, in accordancewith the present invention. The system includes a process chamber 100within which semiconductor wafers are rinsed, decontaminated, and dried,a deionized (DI) water source 101 for rinsing the wafers, and anisopropyl alcohol (IPA) source 102 and nitrogen source 104 fordecontaminating and drying the wafers. Following the rinsing step, wasterinse fluid from the process chamber 100 is rapidly drained throughmultiple drain lines 218 (described below) into a buffer tank 220 usinga “quick-drain” process. The quick-drain process is described in furtherdetail below. The buffer tank releases the waste rinse fluid through adrain line 224, and the waste fluid is treated in a waste facility. Inaddition, organic gases, for example IPA gases, are exhausted from theprocess chamber, for example, at exhaust ports 217 (described below),and treated at a scrubber 225 to prevent fire and release of toxins.

The following process is described below with additional reference tothe flow diagram of FIG. 9. To initiate the cleaning and drying process,the wafers to be processed are loaded into the process chamber 100. Arinsing operation is performed to remove process chemicals, for exampleetch chemicals. DI water provided by source 101 flows into the chamberprior to, or following, placement of the wafers so as to submerge thewafers. In one example, the DI water rinse fluid comprises hydrofluorine(HF)-buffered DI water. Alternatively, commercial cleaning solution,such as SC1, maybe used. The DI water flow continues, causing theprocess chamber to overflow, thereby thoroughly rinsing the surfaces ofthe wafers (step 402).

Following this, the DI water is rapidly drained from the process chamber100, using the “quick-drain” apparatus described below, for example thedraining tubes placed in less than about 50 seconds, and preferablywithin about 7-17 seconds (step 404). To accommodate the quick-drain,the DI water is released via a plurality of wide, evenly distributed,drain apertures into a buffer tank 220 that lies below the processchamber 100. The buffer tank 220 temporarily holds the waste fluid untilit can be properly disposed via drain line 224.

In the decontamination step, the lid of the process chamber 100 isclosed, gas exhaust ports of the chamber are opened (step 406), and aflow of heated IPA vapor from source 102 is delivered to the processchamber 100 to initiate the wafer drying process, and to further removecontaminants, for example contaminants in the form of particles, fromthe surfaces of the wafers (step 408). In one example, the heated IPAvapor 102 flows for about 90 seconds. The IPA vapor is delivered to theprocess chamber 100 using nitrogen 104 as a carrier vapor. In thepresent invention, during the decontamination step, the flow rate ofnitrogen vapor is precisely controlled, in order to provide the processchamber environment with an optimal IPA-to-nitrogen ratio, which, inturn, provides for optimal cleaning, drying and removal of watermarksfrom the wafers.

In one example, the flow rate of nitrogen vapor is controlled byproviding, in addition to the “carrier” nitrogen vapor flow used todrive the IPA vapor, a second, independent source of heated nitrogen gasinto the process chamber 100 to ensure the proper IPA-to-nitrogen ratioin the chamber 100 (step 408). This second source of nitrogen isreferred to below as the “purge” nitrogen vapor, since the second sourcecan optionally later be used to purge the process chamber during thesubsequent drying step. It should be noted, however, that the firstsource, or “carrier” nitrogen source, can also be used for thesubsequent drying step, as described below. It has been determined thatrapid draining of the DI water bath, during the rinsing step, combinedwith an optimized IPA-to-nitrogen ratio during the decontamination step,lead to optimal removal of particles from the wafers, as describedbelow.

The IPA decontamination vapor of the decontamination step may beintroduced during the quick-drain of the rinsing fluid, or, preferably,is introduced following completion of the quick-drain procedure.Experimental data indicates that IPA introduction following completionof the quick-drain procedure results in fewer particles remaining on thewafers. During the decontamination step, the plurality of drain linesfrom the process chamber 100 to the buffer tank 220 remain open. Inaddition, multiple gas exhaust lines 217 in the process chamber,described in further detail below, are open during this step. Theoperation of the multiple gas exhaust lines is described in furtherdetail below.

Following this, heated nitrogen vapor, for example from the secondnitrogen vapor source, is sprayed onto the wafers to dry the wafers(step 410). In one example, the nitrogen flow is activated forapproximately 300 seconds. Again, during this step, the plurality ofdrain lines from the process chamber 100 to the buffer tank 220, as wellas the gas exhaust lines, remain open in order to maintain uniformpressure in the chamber and to remove IPA from the chamber at the sametime.

Following this, the process chamber exhaust lines and drain lines areclosed. The lid of the chamber is then opened, and the cleaned and driedwafers are removed.

FIG. 3 is a schematic block diagram of a first cleaning and dryingsystem for cleaning and drying semiconductor wafers in accordance withthe present invention. In this embodiment, a first flow of nitrogen isprovided by a first nitrogen source 104A. The rate of flow of the firstnitrogen source 104A is controlled by a first mass flow controller (MFC)183, in which an electrical signal is used to maintain a suitable flowrate.

The controlled flow of the first nitrogen source is heated by a firstheater 106A to an appropriate temperature. A second flow of nitrogen isprovided by a second nitrogen source 104B. The rate of flow of thesecond nitrogen source 104B is controlled by a second mass flowcontroller (MFC) 182. The controlled flow of the second nitrogen sourceis heated by a second heater 106B to an appropriate temperature. An IPAsource 102 is coupled to an IPA tank 120. A filter 126 is provided forpurifying the IPA solution prior to entry into the tank 120. Valve 185enables the flow of IPA solution to the IPA tank 120.

IPA solution in liquid form pools in the bottom of the IPA tank 120. Aheater 122 in the base of the IPA tank 120 vaporizes a portion of theIPA solution to generate an IPA vapor that resides above the solution.

As stated above, during an IPA-based decontaminating procedure, the IPAvapor located in the IPA tank 120 is transported into the processchamber 100 by the first flow 104A of heated nitrogen gas, i.e. the“carrier” nitrogen supply. During this step, valves 112 and 116 are openand valve 114 is closed. The nitrogen gas heated by the heater 106Aflows through valve 112 into the IPA tank 120, where it reacts with theIPA vapor in the tank 120. The IPA vapor is then transported by theincident nitrogen vapor through valve 116, into the process chamber 100.An optional line heater 130 heats the combined nitrogen and IPA vaporsupplied at line 191 to a predetermined temperature prior to entry intothe process chamber 100. The line heater comprises, for example, aquartz plate/heating coil/quartz plate configuration which envelops thegas line. The line heater 130 maintains the temperature of the gasesentering the process chamber 100, in order to increase the reliabilityof the semiconductor manufacturing process.

At the same time, during the IPA-based decontaminating procedure, inorder to precisely control the IPA-to-nitrogen ratio of thedecontaminating vapor entering the process chamber 100, a second sourceof heated nitrogen supplied at line 193 from the second nitrogen source104B is provided, referred to above as the “purge” nitrogen source. Asstated above, the rate of flow of the second source of nitrogen isprecisely controlled, for example by the second MFC 182, in order toensure the proper ratio. The vapor provided by the second source 104B atline 193 is also heated by the line heater 130, where it is mixed withthe combined nitrogen/IPA vapor from line 191. Together, the first andsecond vapor sources arriving via lines 191 and 193 are provided to theprocess chamber 100 via line 195.

In a preferred embodiment, the line heater 130 heats the applied vaporsuch that it is released at line 195 at a temperature of about 130C. Atthe same time, the first heater 106A operates to heat the first nitrogengas source 104A to a temperature of about 100C-120C, the second heater106B operates to heat the second nitrogen gas source 104B to atemperature of about 130C-150C, and the IPA tank heater 122 operates toheat the IPA solution in the tank to a temperature of about 50C to 70C.The operating temperature of the first heater 106A is preferably lowerthan the operating temperature of the second heater 106B, because alower temperature is required for precisely controlling the deliveryrate of the IPA vapor from the IPA tank 120.

As stated above, during the drying step, heated nitrogen gas flowsdirectly into the process chamber 100, for volatizing any condensed IPAremaining on the wafers. During this step, valves 112 and 116 areclosed, and valve 114 is open. The second “purge” nitrogen source 104Bmay optionally be used in conjunction with, or instead of, the firstnitrogen source 104A for this step.

As an optional entry configuration for the heated nitrogen gas into theIPA tank, dual entry ports 124A, 124B may be provided. The first port124A lies above the surface of the IPA solution in the tank, to serve asa pressurized transport mechanism for the IPA vapor lying above thesolution surface, as described above. The second port 124B enters theIPA tank below the surface of the IPA solution, and mixes, or bubbles,directly with the IPA solution, to further activate the reaction withthe IPA solution. In this manner, the interaction of the IPA solutionwith the nitrogen carrier vapor is enhanced.

FIG. 4 is a schematic block diagram of a second cleaning and dryingsystem for cleaning and drying semiconductor wafers in accordance withthe present invention. This embodiment is similar in structure andperformance to those of the first embodiment described above inconnection with FIG. 3. However, in this embodiment, an additional flowline 134 is connected between the line 193 providing the heated secondnitrogen source and the entry ports 124A, 124B of the IPA tank 120. Thisflow line 134 allows the second nitrogen source 104B to serve as a“carrier” vapor source for the IPA tank, for example to allow forservicing of the first MFC 183 or the first heater 106A without havingto disrupt system operation. In this case, valve 132 is closed, valve112 is closed, and valve 128 is open. At the same time, the firstnitrogen source 104A may be directly applied to the process chamber 100,by opening valve 114 to initiate flow via line heater 130, after beingmixed with the IPA/nitrogen vapor mixture at line 191. The roles of thefirst and second nitrogen sources 104A, 104B are thus temporarilyreversed in this example to allow for servicing of the first MFC 183and/or the first heater 106A.

In addition, this second embodiment provides an optional line 187 andrelated valve 187A that combines the first and second nitrogen sources104A, 104B. It should be noted that while the first and second nitrogensources 104A, 104B are illustrated as different, independent sources,they may, in fact comprise a common source that has two outlets, theflow of each outlet being independently controlled, for example by thefirst and second MFC's 183, 182. In this case, the common source shouldmaintain a pressure great enough to source the combined flow rate of theMFCs 183, 182.

FIG. 5 is a block diagram of the process chamber 100, including adraining system that provides for rapid draining of the chamber inaccordance with the present invention. The process chamber 100 includesa bath 210 capable of processing multiple wafers, for example 50semiconductor wafers 212, at a time. The wafers are supported by support214. At a bottom region 216 of the bath 210, a plurality of drainopenings 219 are provided. A plurality of exhaust port openings 217 arealso provided. The respective drain openings 219 are relatively wide incross section to allow for rapid draining of fluid, for example, the DIwater fluid, from the bath 210. The drain openings 219 are coupled tomultiple drain lines 218, which transport the rapidly discharged fluidinto a buffer tank 220. The buffer tank preferably has a volume at leastas large as the volume of the bath 210, so that it can receive theentire content of the bath liquid all at once, without hindering theflow of liquid.

The multiple drain openings 219 and multiple drain lines 218, arepreferably distributed across the lower side 216 of the bath 210. Thisconfiguration ensures that, during draining, the fluid being drainedremains level and flat as it is drained, in turn ensuring the sameexposure time for the different wafers being processed in the bath,irrespective of where the wafers are located in the bath 210 relative tothe drain outlet 219. This feature overcomes a funneling phenomenon thatwould otherwise occur if a single drain were to be used, which wouldlead to different exposure times for the different wafers, the exposuretimes corresponding to their positions relative to the single drainlocation.

Similarly, the multiple exhaust ports 217 are included in the bath forensuring an even distribution, i.e. laminar flow, of the decontaminatingand drying vapors in the bath 210. Following the quick drain procedure,when the IPA and N₂ gases are introduced for the decontamination step,the multiple exhaust ports 217 are opened to allow for the even flow ofdecontamination vapors across the wafers. This avoids the problemassociated with a single exhaust port, which would tend to concentratethe vapor flow in certain regions of the bath, for example due to eddycurrents. In a preferred embodiment, the exhaust ports 217 remain openduring the decontamination step and the drying step, and are optionallyopen, when needed, during the quick-drain step.

In this manner, the present invention increases semiconductorfabrication productivity. To increase productivity, the drain time of DIwater is aggressively shortened by use of the quick-drain procedure.Watermarks remaining on the wafers as a result of the quick drainprocess are then efficiently removed by precisely controlling the ratioof nitrogen gas to IPA gas during the decontamination procedure. In thismanner, process throughput is enhanced, in a manner that lends itselfwell to high process quality.

FIG. 6 is a chart illustrating remanent particle density as a functionof the rate of flow of nitrogen vapor, in accordance with the presentinvention. An experiment was conducted to determined the effectivenessof the decontamination step where the second, independent heatednitrogen source 104B was included, for improving control over theIPA-to-nitrogen ratio in the decontaminating fluid introduced into theprocess chamber 100. In this experiment, the first heater 106A, secondheater 106B, and line heater 130 were set at a temperature of 130C. TheIPA tank heater 122 was set at a temperature of 65C. The chamber exhaustpressure was set at 75 mmH₂O.

In a first experiment, represented by plot I of FIG. 6, the firstnitrogen source 104A was activated, for driving the IPA vapor, and thesecond nitrogen source 104B was dormant. In this case, optimal flow rateof the first nitrogen source 104A is determined to be at the minimum ofthe curve, or at about 50 liters per minute (LPM), resulting in over 100particles remaining per 300 mm wafer.

In a second experiment, represented by plot II, the first nitrogensource 104A and second nitrogen source 104B were both activated, thefirst source 104A being set at 20 LPM for driving the IPA vapor, and thesecond source 104B for supplying additional nitrogen into the processchamber 100 for improved control over the IPA-to-nitrogen ratio in thechamber. In this case, the minimum of the plot II curve fell over arange of about 40-70 LPM flow of the second nitrogen source 104B, forwhich particle density was on the order of less than 30 particlesremaining per 300 mm wafer.

FIG. 7 is a chart illustrating remanent particle density as a functionof drain time, in accordance with the present invention. Assuming theconditions of the above experiment, with the first nitrogen source 104Aoperating at a flow rate of 20 LPM, and with the second nitrogen source104B operating at a flow rate of 50 LPM, and assuming 140 cc of IPAbeing used for the decontamination step, remanent particle density wasdetermined as a function of drain time. It can clearly be seen in thechart that as drain time is reduced, the remanent particle densityimproved. In the range of 7-17 seconds of drain time, particle densitywas on the order of less than 20 particles remaining per 300 mm wafer.

FIG. 8 is a chart that illustrates the selection of optimal flow ratesfor the first “carrier” nitrogen source 140A and the second “purge”nitrogen source 140B, in accordance with the present invention. Inregion 308 of the chart, the carrier nitrogen source is at too small ofa flow rate to properly dry the wafers. In region 310 of the chart, toomuch carrier nitrogen is present, and, as a result, too much IPA vaporis presented to the wafers, resulting in IPA gel formation on the wafersand in the process chamber. Regions 302 and 304 of the chart indicatepreferred combinations of carrier nitrogen and purge nitrogen levelsthat lead to preferred IPA-to-nitrogen ratios in the process chamber.Arrow 303, for example, indicates a carrier nitrogen flow rate of 10 LPMand a purge nitrogen flow rate of 100 LPM. An optimal condition existsat the intersection of the charts at point O 306, where the carriernitrogen flow rate is 20 LPM and the purge nitrogen flow rate is 50 LPM.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade herein without departing from the spirit and scope of the inventionas defined by the appended claims.

1. A system for processing semiconductor wafers comprising: a firstinlet for a first supply of drying fluid; a second inlet for a secondsupply of drying fluid, a rate of supply of the second supply of dryingfluid being independent of that of the first supply of drying fluid; adecontaminating fluid tank for storing a supply of decontaminatingfluid, the decontaminating fluid tank having an inlet for receiving thesecond supply of drying fluid, and having an outlet for supplyingdecontaminating fluid at a rate that is based on the rate of supply ofthe second supply of drying fluid; and a process chamber for housing thesemiconductor wafers to be cleaned and dried, the process chamber havingan inlet for simultaneously receiving the first supply of drying fluidand the supply of decontaminating fluid.
 2. The system of claim 1wherein the first supply of drying fluid comprises nitrogen gas.
 3. Thesystem of claim 1 further comprising a first heater for heating thefirst supply of drying fluid between the first inlet and the processchamber.
 4. The system of claim 1 wherein the second supply of dryingfluid comprises nitrogen gas.
 5. The system of claim 1 furthercomprising a second heater for heating the second supply of drying fluidbetween the second inlet and the decontaminating fluid tank.
 6. Thesystem of claim 1 further comprising a third heater coupled to thedecontaminating fluid tank for heating the decontaminating fluid in thetank.
 7. The system of claim 6 wherein the decontaminating fluid in thetank is partially heated by the third heater from a liquid into a vaporand wherein the second supply of drying fluid drives the decontaminatingfluid vapor through the outlet of the decontaminating fluid tank.
 8. Thesystem of claim 7 wherein the inlet of the decontaminating fluid tankincludes a first inlet for receiving the second supply of drying fluidat a level below the level of the liquid and a second inlet forreceiving the second supply of drying fluid at a level above the levelof the liquid.
 9. The system of claim 1 further comprising a fourthheater coupled to a line in turn coupled to the inlet of the processchamber for heating the first supply of drying fluid and the supply ofdecontaminating fluid prior to their release into the process chamber.10. The system of claim 1 wherein the first supply of drying fluid andthe supply of decontaminating fluid received at the process chamber arein a vapor state.
 11. The system of claim 1 further comprising acoupling tube for selectively coupling the first supply of drying fluidto the decontaminating fluid tank.
 12. The system of claim 1 furthercomprising a coupling tube for selectively coupling the second supply ofdrying fluid directly to the process chamber.
 13. The system of claim 1further comprising a coupling tube for selectively coupling the firstinlet to the second inlet.
 14. The system of claim 1 wherein the processchamber further comprises a drain.
 15. The system of claim 14 furthercomprising a buffer tank coupled to the drain of the process chamber.16. The system of claim 15 wherein the drain comprises a plurality ofdrains, and wherein the plurality of drains are coupled to the buffertank.
 17. The system of claim 16 wherein the plurality of drains are ofa width to ensure rapid draining of the process chamber.
 18. The systemof claim 16 wherein the plurality of drains are spaced apart in theprocess chamber to ensure that a top surface of a fluid to be drainedfrom the process chamber remains level as the process chamber isdrained.
 19. The system of claim 16 wherein the plurality of drains areof a width to ensure rapid draining of the process chamber within a timeperiod less than about 50 seconds.
 20. The system of claim 16 whereinthe plurality of drains are of a width to ensure rapid draining of theprocess chamber within a time period ranging between about 7 and 17seconds.
 21. The system of claim 15 wherein the buffer tank is of avolume that is greater than or equal to a volume of the process chamber.22. The system of claim 1 further comprising a first supply ratecontroller for controlling the rate of supply of the first drying fluidand a second supply rate controller for controlling the rate of supplyof the second drying fluid, the first and second supply rate controllersbeing independent of each other such that the rate of supply of thefirst drying fluid and the rate of supply of the second drying fluid areindependent relative to each other.
 23. The system of claim 1 whereinthe process chamber further comprises a plurality of exhaust portsdistributed in the process chamber to provide for laminar flow of thedecontaminating fluid and the drying fluid in the process chamber.
 24. Asystem for processing semiconductor wafers comprising: a first inlet fora first supply of drying fluid; a second inlet for a second supply ofdrying fluid, a rate of supply of the second supply of drying fluidbeing independent of that of the first supply of drying fluid; adecontaminating fluid inlet for receiving a supply of decontaminatingfluid; and a process chamber for housing the semiconductor wafers to becleaned and dried, the process chamber having inlets for simultaneouslyreceiving the first and second supply of drying fluid and the supply ofdecontaminating fluid.
 25. A system for processing semiconductor waferscomprising: a first inlet for a first supply of drying fluid; a secondinlet for a second supply of drying fluid, a rate of supply of thesecond supply of drying fluid being independent of that of the firstsupply of drying fluid; a decontaminating fluid inlet for receiving asupply of decontaminating fluid; and a process chamber for housing thesemiconductor wafers to be cleaned and dried, the process chamber havinginlets for simultaneously receiving the first and second supply ofdrying fluid and the supply of decontaminating fluid, wherein anadditional flow line having a valve is attached between the first inletand the second inlet.
 26. A method for processing semiconductor waferscomprising: providing a first supply of drying fluid; providing a secondsupply of drying fluid, a rate of supply of the second supply of dryingfluid being independent of that of the first supply of drying fluid;storing a supply of decontaminating fluid in a decontaminating fluidtank, the decontaminating fluid tank having an inlet for receiving thesecond supply of drying fluid, and having an outlet for supplyingdecontaminating fluid at a rate that is based on the rate of supply ofthe second supply of drying fluid; and simultaneously supplying thefirst supply of drying fluid and the supply of decontaminating fluid toa process chamber to decontaminate semiconductor wafers containedtherein.
 27. The method of claim 26 wherein the first supply of dryingfluid comprises nitrogen gas.
 28. The method of claim 26 furthercomprising heating the first supply of drying fluid prior to release inthe process chamber.
 29. The method of claim 26 wherein the secondsupply of drying fluid comprises nitrogen gas.
 30. The method of claim26 further comprising heating the second supply of drying fluid prior torelease in the decontaminating fluid tank.
 31. The method of claim 26further comprising heating at least a portion of the decontaminatingfluid in the tank from a liquid state into a vapor state.
 32. The methodof claim 26 further comprising heating the first supply of drying fluidand the supply of decontaminating fluid prior to their release into theprocess chamber.
 33. The method of claim 26 wherein the first supply ofdrying fluid and the supply of decontaminating fluid received at theprocess chamber are in a vapor state
 34. The method of claim 26 furthercomprising, prior to simultaneously supplying the first supply of dryingfluid and the supply of decontaminating fluid to the process chamber:supplying rinsing fluid into the process chamber containing thesemiconductor wafers for rinsing the semiconductor wafers; rapidlydraining the rinsing fluid from the process chamber;
 35. The method ofclaim 34 further comprising rapidly draining the rinsing fluid into abuffer tank having a volume that is greater than or equal to the volumeof the process chamber.
 36. The method of claim 34 wherein the rinsingfluid comprises deionized water in a liquid state.
 37. The method ofclaim 34 wherein the rinsing fluid is completely drained prior tosimultaneously supplying the first supply of drying fluid and the supplyof decontaminating fluid to the process chamber.
 38. The method of claim26 further comprising, following simultaneously supplying the firstsupply of drying fluid and the supply of decontaminating fluid to theprocess chamber, supplying a drying fluid into the chamber for dryingthe semiconductor wafers.